GDP turned negative as early as 2008, shrinking by 0.2 percent compared with a previous estimate of 1.0 percent growth, the ELSTAT agency said.

The recession continued throughout 2010, when the economy contracted 3.5 percent, less than the 4.5 percent decline assumed under the previous set of figures.

Economic growth is a key variable in an ongoing debate on whether the country's debt burden is sustainable. EU officials are suggesting that private holders of Greek bonds may have to suffer bigger losses as part of a new bailout.

The revised data supports recent forecasts by Athens and its international lenders that the economy will slump by 5.5 percent this year, more than previously expected, said Nikos Magginas, an economist at the National Bank of Greece.

"A shallower recession in 2010 suggests a deeper one in 2011, due to base effects," Magginas said.

ELSTAT said the revision came about after improved measuring of private household spending, investment and trade data. It did not provide revised quarterly GDP figures and said more details would be announced on October 10.